[Feature] Application Role Connections Metadata support (#2530)

* models & internal methods

* moar stuff

* working `Get` & `ModifyRoleConnectionMetadata`

* comments & dots

* get & modify user's role connection

* Update src/Discord.Net.Core/Entities/ApplicationRoleConnection/RoleConnection.cs

* Update src/Discord.Net.Core/Entities/ApplicationRoleConnection/RoleConnection.cs

Co-authored-by: Casmir <68127614+csmir@users.noreply.github.com>

src/Discord.Net.Rest/API/Common/RoleConnectionMetadata.cs

@@ -0,0 +1,25 @@
+using Newtonsoft.Json;
+using System.Collections.Generic;
+
+namespace Discord.API;
+
+public class RoleConnectionMetadata
+{
+    [JsonProperty("type")]
+    public RoleConnectionMetadataType Type { get; set; }
+
+    [JsonProperty("key")]
+    public string Key { get; set; }
+
+    [JsonProperty("name")]
+    public string Name { get; set; }
+
+    [JsonProperty("description")]
+    public string Description { get; set; }
+
+    [JsonProperty("name_localizations")]
+    public Optional<Dictionary<string, string>> NameLocalizations { get; set; }
+
+    [JsonProperty("description_localizations")]
+    public Optional<Dictionary<string, string>> DescriptionLocalizations { get; set; }
+}